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Bicoloured Hawk

The bicoloured hawk (Accipiter bicolor) is a species of bird of prey in the Accipitridae family. It is found in forest, woodland, second growth, plantations, and wooded savanna in southeastern Mexico, Central America, and northern and central South America (as far south as northern Argentina).[2] Though generally uncommon, it is the most common species of Accipiter in most of its range, but it does not occur at altitudes above 2,700 metres (8,900 ft) such as the highest parts of the Andes.[3]

Description[edit]

At 34–45 centimetres (13–18 in) in length and 200–450 grams (7.1–15.9 oz) in weight, it is significantly smaller than the northern goshawk of Eurasia and North America, and somewhat smaller than the Cooper's hawk of North America, but among the largest Accipiter hawks in Central and South America (only the rare grey-bellied hawk is larger).[3] As in other Accipiter hawks, the female is far larger than the male. Adults are grey above with darker wings and crown, and a banded tail. The underparts typically vary from dark grey to very pale grey, but the southern subspecies can sometimes be rufescent below. The thighs are always pure rufous (not always easily seen), and the underwing coverts are white in the northern subspecies and rufous in the southern.[3] Juveniles are very variable. They can be white, buff or rufous below, and sometimes with dark streaks. Their upperparts are browner than in adults, and the thighs are sometimes paler.[3]

Taxonomy[edit]

The bicoloured hawk is a species in the genus Accipiter and is included in the family Accipitridae. Three subspecies are currently recognized. The bicoloured hawk is also closely related to the Cooper's hawk (A. cooperii) and the Gundlach's hawk (A. gundlachi); these three form a superspecies.[4] Until recently, the Chilean hawk (A. chilensis) from the colder, southernmost South America was treated as a race of A. bicolor but due to its differences in habitat preferences and plumages from the bicoloured hawk, A. chilensis is now considered a full species.[5]

Four subspecies of A. bicolor are acknowledged. These are:

  • A. b. bicolor, which is found in Southeastern Mexico and south through northern South America.[5] Adults have a black crown, slate upper parts and a blackish tail that displays two or three pale bars. The primaries are obscurely barred.[6]
  • A. b. fidens, which occurs in Eastern and Southern Mexico.[5] It is morphologically similar to A. b. bicolor, but is larger in size and darker in color.[6]
  • A. b. pileatus, living in Brazil.[6] Adults are similar to A. b. bicolor, but are much paler and have a pearl-grey collar. Under-wing coverts and thighs are rufous.[7]
  • A. b. guttifer; located in South Bolivia and northern Argentina. The underparts of the adult are grey or extensively salmon rufous with large white spots and bars.[7]

Habitat and distribution[edit]

Bicoloured hawk. Biological station La Selva, Costa Rica

The bicoloured hawk is widespread but uncommonly observed. Its range extends from Mexico to west Ecuador, the Guianas to Colombia, south to east Peru, through Amazonian Brazil to Paraguay, north-north western Argentina, Bolivia and to Chile.[8] It mainly resides in forests, along forest edges and in clearings in tropical and locally subtropical zones,[7] although its habitat is none too specialized. It may also reside in rain forest, drier, thinned forest, and palm savanna with gallery forest.[4]

Forest disturbance and fragmentation negatively affect the habitat and quantity of the bicoloured hawk, which is most abundant in primary undisturbed forest or riparian forest. There are fewer hawks in disturbed habitats such as forests that have been logged, and even fewer in those fragmented habitats that provide greater than 66% forest cover. These hawks are rarely present in forests that provide less than 66% forest cover.[9]

Behaviour[edit]

The bicoloured hawk is difficult to detect due to its shyness and inconspicuousness. Because of this behaviour, the bicoloured hawk may be more common than it seems.[10]

Vocalisations[edit]

Its vocalisations are mainly subdued and unnoticeable. Males have been heard to give a soft, clear whistle and females can emit a loud "cac cac cac" when around the nest and young.[6] A barking "kra-kra-kra-kr-kr-kr-ka" may also be heard from both sexes.[11] During incubation, males give a sharp "kek" vocalisation upon arrival to the nest with food, to which the female replies with a nasal "wreh".[12]

Diet[edit]

These hawks capture prey in a stealthy manner by flying through dense vegetation to ambush unsuspecting prey. They may also capture prey through aerial pursuit after inconspicuously sitting and watching their target.[13] At times, the bicoloured hawk may hunt in pairs. Most commonly, it feeds on smaller birds such as thrushes and small doves[3] but has also been known to consume small mammals and reptiles.[12] Several instances where the hawks attack groups of squirrel monkeys or tamarins have been witnessed. In addition, these hawks may follow groups of monkeys in order to feed on the insects that are exposed by the monkeys.[4]

Reproduction[edit]

Bicoloured hawks breed in forest areas, choosing to build nests on tree branches and occasionally hanging vines. The nest is built in cooperation between the male and female and is constructed from dried sticks and leaves. Each breeding pair will normally build a new nest at the beginning of each breeding year. Copulation occurs after breeding activities such as feeding and nest building have been completed. Egg laying takes place approximately five weeks after copulation and the dull white eggs measure an average of 47.1 mm × 36.5 mm; clutches average 1–3 eggs.[14] The eggs are brooded for about three weeks by the female while the male forages for food. Bicoloured hawk chicks are categorized as semi-altricial; the eyes are open at hatching but the chicks are not immediately mobile and are fed by the parents.[15] The young fledge around 30–36 days after hatching and the fledgling period spans nearly seven weeks, during which the young will return to the nest frequently for food until they become independent.[12]

References[edit]

  1. ^ BirdLife International (2012). "Accipiter bicolor". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ Stotz, D.; Fitzpatrick, J. W.; Parker, Theodore A., III; Moskovits, Debra K. (1996). Neotropical Birds: Ecology and Conservation. Chicago: University of Chicago Press. ISBN 0-226-77630-1. 
  3. ^ a b c d e Ferguson-Lees, J.; Christie, D. A. (2001). Raptors of the World. ISBN 0-7136-8026-1. 
  4. ^ a b c del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi, eds. (1994). Handbook of the Birds of the World II. ISBN 978-84-96553-45-3. 
  5. ^ a b c Accipiter bicolor. Globalraptors.org (2012-07-27). Retrieved on 2013-04-03.
  6. ^ a b c d Brown, L.; Amadon, D. (1968). Eagles, Hawks and Falcons of the World 2. New York: McGraw-Hill Book Company. 
  7. ^ a b c Blake, E. R. (1977). Manual of Neotropical Birds. Chicago: University of Chicago Press. ISBN 0226056414. 
  8. ^ de Schauensee, R. M. (1970). A Guide to the Birds of South America. Wynnewood: Livingston Publishing. ISBN 0-87098-027-0. 
  9. ^ Juliien, M.; Thiollay, J.M. (1996). "Effects of Rain Forest Disturbance and Fragmentation: Comparative Changes of the Raptor Community Along Natural and Human-Made Gradients in French Guiana". Journal of Biogeography 23 (1): 7–25. doi:10.1046/j.1365-2699.1996.00963.x. JSTOR 2846013. 
  10. ^ gavião-bombachinha-grande (Accipiter bicolor) | WikiAves – A Enciclopédia das Aves do Brasil. WikiAves (2009-07-11). Retrieved on 2013-04-03.
  11. ^ Hilty, Steven (2003). Birds of Venezuela. Princeton: Princeton University Press. ISBN 0691092508. 
  12. ^ a b c Thorstrom, R.; Quixchan, A. (2000). "Breeding biology and nest site characteristics of the Bicoloured Hawk in Guatemala". Wilson Bulletin 112 (2): 195–202. doi:10.1676/0043-5643(2000)112[0195:BBANSC]2.0.CO;2. ISSN 0043-5643. JSTOR 4164195. 
  13. ^ Overview – Bicolored Hawk (Accipiter bicolor) – Neotropical Birds. Neotropical.birds.cornell.edu. Retrieved on 2013-04-03.
  14. ^ Thorstrom, R.; Kiff, L. F. (1999). "Notes on Eggs of the Bicolored Hawk Accipiter bicolor" (PDF). Journal of Raptor Research 33 (3): 244–247. 
  15. ^ Parental Care. People.eku.edu. Retrieved on 2013-04-03.

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